ISCOMs/MPLA adjuvanted SDAD protein nanoparticles induce improved immune responses and cross-protection in mice

Abstract

Abstract The development of a universal influenza vaccine to protect against influenza variants will be the priority goal in combating influenza virus infection. In this study, we exploited a novel type of protein nanoparticles consisting of influenza NP as the core and NA1-M2e or NA2-M2e fusion proteins as the coating antigens by using an SDAD heterobifunctional crosslinker. Intramuscular immunization of the NP/NA-M2e (core/shell) nanoparticles induced increased humoral and cellular immune responses. ISCOMs/MPLA as adjuvants further improved the nanoparticle immunogenicity and elicited stronger immune reactions conferring protection against different influenza viral challenges. The nanoparticles were delivered through intranasal route to determine the application as a mucosal vaccine. While the nanoparticles alone barely induced immune response after intranasal immunization, ISCOMs/MPLA adjuvanted nanoparticles induced strengthened antigens-specific antibodies responses, cellular responses and higher levels of mucosal IgA. Meanwhile, increased lung Trm, Brm , and alveolar macrophages, were observed from ISCOMs/MPLA adjuvanted nanoparticle group. Only the mice intranasally vaccinated with ISCOMs/MPLA adjuvanted nanoparticles fully survived during the infections, and better protection efficacy was observed when compared with other adjuvants. Our results emphasized the importance of supplementing of appropriate adjuvants to improve the immunogenicity and mucosal immune responses of vaccines in mucosal immunization. In conclusion, the ISCOMs/MPLA adjuvant combination could significantly improve the immune responses and protective efficiency of protein nanoparticles in different immunization routes.